Ha Ha! Just the kind of post you've been looking for?!
Just been building a PC for someone with Windows Vista 32-bit, and a horrible Blue Screen (BSOD) came up on shutdown (forcing a restart), with the message (amongst other things):
MULTIPLE_IRP_COMPLETE_REQUESTS
The Microsoft site and other searches led me to believe that it was probably an unsigned driver error - and yes, I'd installed a modem with the "Intel V92 HaM" driver. This has compatibility problems with Vista. Took it out - and bingo! All is fine.
Moral:
(1) Double check all components for Vista compatibility. Assume nothing! Make sure you can see Vista drivers on their website.
(2) if you get the MICR BSOD, it's probably some naff card you've installed!!